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November's 3 Biggest Biotech Busts

Sarepta's huge drop leads a field of monthly losers that includes Aegerion's drop and Immunogen's plunge.

The biotech sector can burn investors just as easily as it can reward them, but it's been much more of the latter than the former in 2013. The Nasdaq Biotechnology Index has jumped 8% since November kicked off alone, part of a 58% year-to-date climb. It's safe to say that biotech's been an investor's dream this year.

But not every stock in this industry has been a blessing. Several notable biotech stocks have burned investors in a big way in November, sinking into the red despite the industry's overall gains. Let's take a look at three of November's biggest biotech losers, highlighted by big losses at Sarepta(NASDAQ:SRPT). Can these falling stocks rebound in the future?

Immunogen's losses shouldn't shake investorsImmunogen(NASDAQ:IMGN) leads off the countdown, as this biotech stock's taken a big hit over the past month. Shares have fallen more than 13% over the past month, paring Immunogen's year-to-date gains that hadn't disappointed until November kicked off. Immunogen's bounced around all month, set off by two big days -- one bad for investors, one good.

The company first disappointed investors early on in the month when it cancelled a mid-stage trial of its developmental small-cell lung cancer drug IMGN901. The drug didn't perform well in its trial, according to Immunogen. Investors bailed on the stock and sent shares down by 19% in a single day. However, as fellow analyst Brian Orelli notes, small cell lung cancer isn't an easy ailment to treat. Failure's no good for the company, but the drug's success was never a guarantee.

Investors who got in on the dip walked away with a big return just a few days later, as it turned out. The stock soared after Novartis agreed to license Immunogen's TAP technology, something that could result in a big payday through royalties for the company. Immunogen's done well in the past helping larger drugmakers develop new therapies -- its most recent success being helping develop Roche's cancer treatment Kadcyla -- but this company will need to keep working to develop a wholly owned drug of its owned in the future if it wants to make a big splash with investors. Still, Immunogen's hardly given reason to panic for investors, despite its big drop in November.

Aegerion(NASDAQ:AEGR) has taken a bit bigger of a hit this month. Shares of this biotech have plunged by more than 16% even after making somewhat of a comeback in the latter part of November. Still, investors hardly have been shaken by this stock's monthly drop. Aegerion's shares have exploded for a 160% gain through 2013 so far, and November's dip barely has touched those returns.

Aegerion's CEO sparked the month's drop after showing up on CNBC and promoting the firm's cholesterol-fighting treatment Juxtapid. The FDA showed up at Aegerion's door soon after, claiming that the company had gone too far and had promoted Juxtapid as capable of treating conditions it had yet to be approved for. Oops! The FDA's warning letter spooked investors for a big drop, but shares bounced back just days afterwards. Considering that the company quickly came out with a statement saying that it will fully comply with the FDA's decisions, this seems only a bump in the road for Aegerion's stellar gains so far this year. Investors shouldn't be worried about this stock's November fall.

Sarepta(NASDAQ:SRPT) investors, however, have a lot more to worry about. This stock's topped all of biotech's losers in shedding more than half of its value in November after being obliterated for a 60% drop in one fateful day.

The FDA noted on Nov. 12 that Sarepta's Duchenne muscular dystrophy drug eteplirsen might not have enough suitable clinical data to pass regulators with the trial the company had been working on for the drug. Regulators advised Sarepta to push eteplirsen against a placebo in a larger study, particularly in light of a rival drug that had failed in a similar study to Sarepta's original trial.

As fellow analyst Keith Speights notes, Sarepta's best bet looks to be to head back to the drawing board with a new trial that will be enough to win over regulators. For investors who had been excited by the prospect of a potential approval of eteplirsen in a year or two, however, November's FDA blow has taken all of the wind out of Sarepta's sails. Now it's time to wait and see whether or not Sarepta can get eteplirsen moving again with a new trial -- and any potential approval, obviously, is far away at this point.